Coral reef habitats strongly influence the diversity of macro-and meiobenthos in the Caribbean

Macro- and meiobenthos contribute substantially to the diversity of marine habitats and should account for a significant fraction of the diversity in coral reefs. The aims of the present study are to characterize macro-and meiobenthic communities in a Caribbean coral reef and to analyze the effects of habitat type on the alpha-, beta-, and gamma-diversity of free-living nematodes. Two reef sites with four habitat types each were selected: seagrass bed, bare sand, coral rubble, and algal turf. Habitats within sites were adjacent to each other and characterized by their physical architecture, hydrodynamic regime, and foundation species. The diversity of marine communities was high, with eight phyla represented in the macrobenthos and 18 phyla in the meiobenthos. The structure of macrobenthos was strongly associated with the habitat type. This relationship was weaker for meiobenthos, which is likely related to ecological drift, hydrodynamic regime, and macrobenthic influence. The nematode species richness was high at both studied scales: alpha-diversity ranged from 31 to 83 species per habitat and gamma-diversity for the whole reef was 156 +/- 4 species. The nematode assemblages consisted of few dominant and many rare species, which is typical of hyperdiverse faunas. The beta-diversity was large in the reef with few shared species and the presence of distinctive nematode assemblages adapted to the physical architecture and food availability of each habitat. The results imply that the physical structure and heterogeneity of the coral reef habitats are important for maintaining the high diversity of small invertebrates, especially regarding the richness and turnover of nematode species.